Froth flotation concentration of potash ores containing sylvite



United States Patent FROTH FLOTATION CONCENTRATION OF POTASH ORES CONTAINING SYLVITE William Aubrey Smith, Carlsbad, N. Mex., and Vernon L. Mattson and Gene Meyer, Lakewood, Colo., assignors to The {American Metal Company, Limited, a corporation of New York No Drawing. Application April 24, 1952, Serial No. 284,197

5 Claims. 01. 209-466) .process in which chemical reagents of the cationic group are used as collectors for the sylvite values. The cationic group of collectors includes the high molecular weight aliphatic amines and their water-soluble amine salts, as well as quaternary ammonium salts. The following are typical examples of the cationic collectors that are commercially available: n-octylamine, n-decylamine, ndodecylamine, n-tetradecylamine, n-hexadecylamine and n-octadecylamine, mixtures of the above mentioned amines in various proportions and the water-soluble acetate salts of such amines.

As borne out by statements found in various prior patents, it was considered necessary, until our recent investigations were made, to use a relatively high proportion of one of the cationic collectors in order to insure an acceptable concentration and recovery of the sylvite ores by a froth flotation process. When treating an ore ficiently effective to prepare the coarser particles of the ore feed for a flotation treatment.

We have further observed that if ore that has been previously ground sufliciently to bring all of the particles within a particle size range such that the coarsest particles will be floated, is treated with the amines by adding the amines in stages, with appropriate agitation between the successive additions to insure dispersion of the amines throughout the ore pulp, the tendency for excess absorption of the amines by the finer particles is reduced and that a satisfactory flotation result may be insured by using a much smaller overall quantity of amines than has heretofore been considered necessary.

According to a preferred embodiment of the invention the ore is first crushed or ground to a suitable degree either to bring all of the particles within a size range suitable for flotation or to a predetermined coarser size and then feed prepared by crushing or grinding to the fineness nor- 4 mally considered necessary in bringing about a froth flotation concentration of the sylvite values, proportions of the amine collecting agent of the order of 0.8 to 1.0 lb. per ton of ore have been generally specified. When it is borne in mind that sylvinite ores generally contain only from30 to 40% of sylvite and that the recovery is not complete, it will be understood that the reagent cost represents a substantial item of the overall cost of recovering sylvite from its ores and producing an acceptable commercial potash product.

It is an object of the present invention to reduce the reagent cost without impairing the flotation result.

We have observed that the tendency for sylvite-containing potash ores to consume an inordinate amount of an amine collector is to a considerable extent due to the tendency of the finer particles of the ore as customarily prepared for the flotation treatment to consume a much larger proportion of the amine than is necessary for a satisfactory flotation result. Furthermore, the finer particles show this capacity for consumption of the amine equally as well when the amine is one of the higher molecular weight amines as is the case when lower molecular weight amines are employed. At the same time it is observed that the lower molecular weight, i. e., shorter chain, amines will by themselves sufiiciently condition the finer particles for a flotation operation so that it is not necessary that such fine particles shall have attached to them any of the more expensive longer chain amines. "On the other hand, the shorter chain amines are not sufscreened or classified to separate out a fraction of an appropriate particle size range for the flotation treatment. For best results the flotation feed should be of a fineness such that all particles will pass a 14-mesh sieve. Preferably particles finer than 270 mesh should also be excluded or will have been removed in the course of the preliminary desliming treatment that is usually applied in preparing the ore for the flotation operation.

When treating sylvinite ores from the Carlsbad district it is very important, as a preliminary to the conditioning of the ore for the flotation treatment, to subject it to a thorough desliming to remove the insoluble clay slimes that are invariably present in these ores or to add a suitable slime control agent in suflicient amount to inhibit the tendency of any clay slimes present to react with or otherwise consume the amine collecting agent. The desliming of the ore may advantageously be brought about by applying the procedures disclosed in the copending application Serial No. 266,314, filed January 14, 1952, and covering a joint invention of the inventors named herein and Robert A. Baxter. The process of slime control disclosed in the copending application of the inventors named herein and the said Robert A. Baxter, Serial No. 247,384, filed September 19, 1951, may also be applied in preparing sylvitecontaining potash ores for the flotation treatment of the present invention. In many instances a combination of the procedures of the aforementioned applications Serial Nos. 247,384 and 266,314 may be used to advantage in preparing the ore for the flotation treatment of the present invention.

Assuming that the ore has been prepared for the flotation treatment by a thorough desliming or by the addition of a slime control agent, or both, as above described, it is then further conditioned for the flotation treatment by first introducing into the ore pulp a sufficient quantity of one or several of the shorter chain amines to insure that at least the greater part, if not all of the ore particles, will have been brought into contact therewith during a subsequent conditioning stage involving agitation of the ore pulp to bring about dispersion of the amines throughout the pulp. Because of the tendency of the shorter chain amines to disperse readily in an aqueous medium and their water solubility and free fluidity, as well as the seeming tendency of the finer ore particles to absorb the amines more readily than do the larger particles, the addition of short chain amines in the initial stage of the conditioning treatment insures that the avidity of the finer ore particles for the amines will have been satisfied to the point where the preferential effect of such particles for the amines will no longer manifest itself in a subsequent stage or stages of the conditioning treatment. The ready and uniform distribution of the shorter chain amines throughout the pulp during the initial conditioning step is also observed Patented Oct. 25, 1955 to have a stabilizing effect on the froth, so much so that when the stage addition of the shorter chain amines is followed by a second or successive additions of longer chain amines suflicient to insure that the coarser ore particles will be collected it may be unnecessary to use any other frothing agent, or at least it will be possible to reduce the amount of frothing agent that would otherwise be required.

As above indicated the initial step of adding and dispersing the shorter chain amines through the pulp is followed by addition of an appropriate amount of a longer chain amine or several longer chain amines selected for their ability to collect the coarser particles of the ore and prepare them for the froth flotation. When the conditioning is completed the pulp is subjected to flotation in the conventional way.

If desired, an appropriate frothing agent may be added, and this will be preferred in all of the cases where sufficient of the shorter chain amines is not present to induce the desired degree of frothing. Frothing agents that have been used in our investigations include pine oil, Nonic 218, Dupont Frother B-23, methyl isobutyl carbinol, Pentasol, amyl alcohol, and cresylic acid. Nonic 218 is the commercial name of a composition manufactured by Sharples Chemical Co. and understood to consist principally of a polyethylene glycol tert. dodecylthioether. Dupont Frother B-23 is understood to consist of 40-45% of primary alcohols (principally 2,4-dimethyl pentanol-l), 45-50% of secondary alcohols (principally 2,4-dimethyl hexanol-S), and 812% of unidentified ketones. The addition of small amounts of conventional frothing agents appears to improve the flotation in all cases where the short chain amines are not used.

Because of their relative cheapness, and other things being equal, it will usually be best to use as large a proportion of the short chain amines as is required to uniformly coat the finer particles and, in addition, if necessary, to impart satisfactory frothing properties to the pulp. However, it is to be understood that the invention in its broader aspects is inclusive of stage conditioning operations wherein no short chain amines are used but in which longer chain amines are added in stages, usually with a first addition of amines of medium length, say, n-decylamine, and a later addition or additions of longer chain amines. Such a procedure may be advantageously employed when the ore for the flotation feed has been sized or classified to exclude a part or all of the finer particles, for example those minus 200 mesh.

The invention will be further described with reference to the following examples:

Example 1.--A 1,000 gm. sample of the l4 mesh fraction produced in crushing a mine run lot of sylvinite ore from the Carlsbad district to /2 and then screening over a 14 mesh sieve was made into a pulp with a saturated brine of the ore constituents, then introduced into a Fagergren three liter laboratory flotation cell, agitated for five minutes and then deslimed by settling one minute, siphoning to a depth of 4 /2" from the top of the bowl, then refilling the bowl with saturated brine to the overflow and agitating for one minute. These operations of settling, siphoning, refilling and agitating were repeated four times.

The deslimed sample of ore was then placed in a 6" I. D. glass bottle with sufficient brine to bring the pulp density to 60% solids. A 2% solution of Tergitol TMN 650 in the proportion of 0.10 lb. per ton of ore was added followed by agitation by rolling the bottle at 94 R. P. M. for two minutes. Thereupon, Armac 8D in the proportion of 0.10 lb. per ton of ore was added and the bottle was again rolled for two minutes as before. Then Armac TD in the proportion of 0.16 lb. per ton of ore was added and the pulp was further agitated by rolling of the bottle for thirty seconds. The thus conditioned pulp was then transferred to the Example 2.For comparison purposes an identical sample of sylvinite ore was deslimed and conditioned for flotation in the same manner as described above and with the same reagents and proportions except that only one amine addition was made, this consisting of Armac TD in the proportion of 0.16 lb. per ton of ore. The results were as follows:

Percent Percent Percent K01 Pmduct Welght Weight KC Cont. Conet 336. 1 35. 0 94. 2 33. 8 86. i) Tailing 599. 2 64. 1 8. 0 5. 1 13. 1

It will be observed that in the test involving stage addition of the amines the grade of concentrate was slightly higher and that the recovery was improved by 9.5%.

Example 3.A 1,000 gm. sample of sylvinite ore crushed to 14 mesh in a coffee mill and rolls was made into a pulp, deslimed four times and conditioned for flotation in the same manner and with the same reagents as described in Example 1, but in this case the proportion of Armac 8D added in the first amine addition stage was 0.04 lb. per ton of ore and in the second amine stage 0.12 lb. of Armac TD per ton of ore was added. The results were as follows:

Here again it will be observed that the recovery was substantially increased while the grade of the concentrate remained practically the same.

Example 4.A 1,000 gm. sample of sylvinite ore prepared as described in Example 3 was pulped, deslimed four times and conditioned for flotation in the same manner as described in the preceding examples except that in this case the amines were added in three stages. In the first stage Armae SD was added in the proportion of 0.04 lb. per ton of ore; in the second amine addition stage Armac TD was added in the proportion of 0.04 lb. per ton of ore, and in the third and final amine addition stage a mixture of long chain amines made up of aliphatic chains of 20, 21 and 22 carbons was added in the proportion of 0.08 lb. per ton. The results of the flotation treatment were as follows:

It will be observed that notwithstanding the same aggregate proportions of amine were used as in Example 2 there was a 7.8% improvement in the recovery.

Due to the relative insolubility of the higher molecular weight amines in brine and the difliculty of obtaining a satisfactory dispersion of such amines in brine without violent mechanical agitation, it is usually preferable to take special steps to bring about their dispersion in the pulp. Such dispersion may be facilitated by introducing the amine in the form of a finely divided sprayor through the use of an emulsifying or wetting agent. For example, we have found that a satisfactory dispersion of Armac TD may be effected by use of a conventional drum conditioner provided the Armac TD is mixed with a small proportion of Aerosol 18 and the resulting mixture is added in the form of a dilute aqueous solution. Dupont Frother B-23 also acts as an emulsifying agent and likewise improves the flocculation by minimizing the tendency to the formation of larger flocs.

Armac 8D is the water soluble acetate salt of normal octyl-amine. Armac TD is understood to consist of the water soluble acetate salts of the normal hexadecyl-, octadecyland octadecenyl-amines derived from tallow in the approximate proportions of 30, 25 and 45 parts by weight. Both of these agents are commercial products of Armour & Co.

Tergitol TMN 650 is a polygylcol compound manufactured by the Carbide and Carbon Chemicals Co. It was used in the tests described above both because of its beneficial effects as a slime control agent and also because the collecting action is improved when it is present with the amines. This improvement is believed to be due at least in part to better dispersion of the amines when the polyglycol compound is present. It also improves the frothing characteristics of the treated pulp when added in association with amines as evidenced by the fact that when it is present it is not necessary to add pine oil or a similar frother even when using the longer chain amines.

It will be understood that other cationic collectors useful in floating sylvite from sylvite-containing potash ores may be substituted for the amines. Various other changes may be made in the details of the procedure without departing from the invention which is not to be considered as limited otherwise than as indicated in the appended claims.

We claim:

1. The improvement in the conditioning of sylvite-containing potash ores for froth flotation which comprises introducing the ore in finely divided form into a saturated aqueous solution of the soluble ore constituents to form a pulp, and conditioning the pulp for the froth flotation treatment by adding successive increments of a cationic collecting agent to said pulp in a plurality of separate addition steps all made prior to said flotation, each successive increment being composed principally of higher molecular weight cationic compounds than the preceding increment, and, following each addition step, agitating the said pulp to elfect thorough distribution of the cationic collecting agent therethrough before making the next addition.

2. The improvement in the concentration of sylvite from sylvite-containing potash ores which comprises introducing the ore in finely divided form into a saturated aqueous solution of the soluble ore constituents to form a pulp, preparing the pulp for a' froth flotation treatment by adding successive increments of an amine collecting agent to said pulp, each successive increment being composed principallyof longer carbon chain amines than the preceding increment, and, following each addition, agitating the pulp to effect thorough distribution of the amine collecting agent therethrough before mak ing the next addition, and thereafter subjecting the pulp to a froth flotation treatment.

3. The improvement in the conditioning of sylvitecontaining potash ores for froth flotation which comprises introducing the ore in finely divided form into a saturated aqueous solution of the soluble ore constituents to form a pulp, adding to said pulp a short carbon chain amine collecting agent in an amount suificient to separate by flotation said finer ore particles, agitating the pulp to effect thorough distribution of the amine collecting agent, thereafter adding longer chain amines in an amount suflicient to separate by flotation the larger ore particles, and further agitating the pulp to complete the conditioning of the pulp for a froth flotation treatment.

4. The process as set forth in claim 1 in which a slime control agent of the class consisting of the polyglycols and their ethers is introduced into the pulp and dispersed therein preliminary to the initial step of conditioning with addition of a cationic collecting agent.

5. The process as set forth in claim 2 in which the aliphatic amine used in the initial amine conditioning step is octylamine acetate and a mixture of normal hexadecyl-, octadecyland octadecenylamines is used in a later amine conditioning step.

References Cited in the file of this patent UNITED STATES PATENTS 2,185,224 Ralston Jan. 2, 1940 2,288,497 Tartaron et al. June 30, 1942 2,297,664 Tartaron et al. Sept. 29, 1942 2,322,789 Cole et a1. June 29, 1943 2,410,021 De Vaney Oct. 29, 1946 OTHER REFERENCES Taggart, Handbook of Mineral Dressing (c) 1945, section 12, page 88. (Copy in Scientific Library.)

Flotation Chemicals for Non-Metallic Minerals, by James A. Barr, Rock Products, Dec. 1946, pg. 91. 

1. THE IMPROVEMENT IN THE CONDITIONING OF SYLVITE-CONTAINING POTASH ORES FOR FROTH FLOTATION WHICH COMPRISES INTRODUCING THE ORE IN FINELY DIVIDED FORM INTO A SATURATED AQUEOUS SOLUTION OF THE SOLUBLE ORE CONSTITUENTS TO FORM A PULP, AND CONDITIONING THE PULP FOR THE FROTH FLOTATION TREATMENT BY ADDING SUCCESSIVE INCREMENTS OF A CATIONIC COLLECTING AGENT TO SAID PULP IN A PLURALITY OF SEPARTE ADDITION STEPS ALL MADE PRIOR TO SAID FLOTATION, EACH SUCCESSIVE INCREMENT BEING COMPOSED PRINCIPALLY OF HIGHER MOLECULAR WEIGHT CATIONIC COMPOUNDS THAN THE PRECEDING INCREMENT, AND, FOLLOWING EACH ADDITION STE, AGITATING THE SAID PULP TO EFFECT THOROUGH DISTRIBUTION OF THE CATIONIC COLLECTING AGENT THERETHROUGH BEFORE MAKING THE NEXT ADDITION. 